Indoor air pollution has now become a major health concern, according to recent EPA studies that have reported that indoor air can be over 10 times more polluted than outdoor air. Additionally, home energy costs for heating and cooling already average nearly one-half of total energy costs for dwellings, with such costs headed higher due to recent price increases. This calls for a simple and effective way to ventilate existing tightly built homes or small business so that breathing air can be exchanged on a scheduled basis by bringing outdoor air to flush out stale inside air and where outside air can be used to help heat or cool the interior whenever favorable outside air is available instead of artificially conditioning the same interior air over and over.
The most practical way to accomplish this ventilation process is to use the existing xe2x80x9ccentral air conditioningxe2x80x9d system as much as possible, to pull in and distribute fresh air through the existing air duct delivery outlets and to use the existing air return inlets to transfer the stale interior air out of the interior spaces instead of just re-circulating it, as occurs with normal operation of the conventional central air system.
The addition of mechanical and control components to an existing system allows a conventional central air unit to selectively operate in this way. The new system can be activated both manually for a desired period of operation and automatically to sense and use outdoor air to assist in heating or cooling when possible and to schedule user-desired indoor air change frequency and volumes of fresh air inputs at the most efficient and effective time periods.
The new ventilation method is active rather than passive, as in opening windows. Even opened windows have negative consequences and are not very effective for changing interior air. Open windows require routine manual operations by the home owner, allow dust, dirt and even rain in and, if not closely monitored, invite intruders. Open windows also defeat many security systems.
Outside air can be xe2x80x9cblendedxe2x80x9d into the recirculated interior air by connecting an opening in the duct system to outside air. That is, in a sense, just putting an xe2x80x9cair leakxe2x80x9d in an existing home that has been built air-tight to lower the heating and cooling expenses is not very effective in actually flushing out the stale interior air and replacing it in a short time with fresh outside air. In cold climates, such blend units are often xe2x80x9cheat exchangersxe2x80x9d in that they have heat transfer surfaces extending from the heated outlet air over into the incoming cold outside air in order to pass some of the interior heated air energy over to the incoming unheated air. These units are relatively expensive and are not very efficient in the more moderate climates with less extremes of cold outdoor temperatures. Blending in fresh air can only dilute contaminated air, not remove it, especially if new pollutants are being introduced from the same inside sources.
The so-called xe2x80x9cwhole house exhaust fansxe2x80x9d that were frequently used before central air systems became routine were and can be more effective in changing the inside air by drawing in larger amounts of fresh air through opened windows while pulling stale interior air out through a wall or attic fan discharge vent. Since the air tends to flow from the open window directly to the fan outlet, however, xe2x80x9cdeadxe2x80x9d areas of stale air continued to exist. Such fans are rare these days since they are noisy in operation, are difficult to seal and tend to leak, and require the manual opening and closing of windows to operate which lets in unfiltered air containing dust and dirt. Opened windows also can be of a security threat in that they offer an invitation to intruders and also defeat security systems.
A central air conditioning and ventilating system has a central air conditioning system in a building having a central air handler having a blower and a heat exchanger therein and a plurality of ducts coupled to the central air handler for receiving forced air therethrough from the blower for distribution to a plurality of areas in the building. A central air conditioning system also has an outside condenser unit coupled to the central air handler heat exchanger and at least one interior return air duct. An exterior air intake duct is coupled between the exterior of a building and the central air handler. Improvements include a first damper positioned in the exterior air intake duct having an open position for opening the duct to the exterior air and a closed position for blocking exterior air from reaching the central air handler. A second damper is positioned in the interior of the return air duct and has an open position allowing interior air to pass therethrough to the air handler and a closed position blocking the interior air from passing through the interior return air duct and a third damper is positioned in the interior return air duct escape air duct and has a closed position for blocking the escape of air from the interior return air duct and an open position, opening said return air duct for venting said return air from a building. The first damper can be opened while the second damper is closed and a third damper opened to convert the air conditioning system to a whole house ventilation system.